Elongated cylindrical drawing element and method for treating yarn thereon



Dec. 11, 1962 T. Y. A=- 3 ,067,460

ELONGATED CTLINDRIEAL DR ING ELEMENT AND 7 METHOD FOR TREATING YARN THEREON Filed Sept. 20, 1960 FIG.! FI6.2

A YARN BOTTOM TUBE LENGTH TOP INVENTOR *m TIN YAM AU ATTORNEY Stat Unite This invention relates to the process of drawing synthetic fibers and more particularly to obtaining the proper temperature gradient on a drawing tube in such a process.

'Artificial fibers, such as those spun from melts of the linear polyamides, possess an incompletely developed tensile strength and a high elongation as extruded from the forming spinneret. It has been found that the tensile strength may be greatly increased and the elongation characteristic reduced by a process of cold drawing whereby the yarn or monofilaments are stretched, often in excess of 600% of their original lengths at some temperature below the yarn melt point.

In the early processes for cold drawing, for example, the method taught by Babcock in US. Patent 2,289,232, the yarn is heated by some heating means and then drawn by a subsequent means such as a snubbing pin. Recently it has been found that more uniform characteristics are obtained when the heating and drawing are done simultaneously. In order to accomplish this, a critical temperature gradient is required on this combination heating and drawing means, such as a drawing tube or pipe, since it is required that the yarn be initially heated to the proper drawing temperature. But immediately after the yarn reaches the proper drawing temperature, the additional heat generated by the friction of the moving yarn against the tube and the additional heat released by the exothermic reaction of drawing must be removed so that the yarn is not overheated and the desired properties lost.

Various methods of obtaining the desired temperature gradient have been tried in the past without success. Multiband electrical heaters with separate controls failed because of insufficient heat removal at the drawing section of the tube. Multisectioned oil heaters, each section having individual control, could be made to perform experimentally, but this system is too complicated and expensive to maintain in a production facility, particularly when these draw tubes are used on a production process where many tubes are used on a single machine.

The principal object of this invention is to provide a simple, efiective, yet economical method and apparatus for controlling the temperature gradient on a draw tube.

Another object of this invention is to provide a method of controlling the temperature gradient on any tube or device where an exothermic reaction is involved.

In general, the objects of this invention are accomplished by providing a narrow annular section in the draw tube through which fluid is passed at the controlled rate so as to obtain the desired temperature gradient along the tube.

In the accompanying drawings,

FIGURE 1 is a general side elevational view of a typical yarn tube, which may be used in carrying out the present invention.

FIGURE 2 is a graph of the temperatures of the tube and the yarn along the yarn tube length.

FIGURE 3 is an enlarged side elevational view, partly in longitudinal cross section, of the draw tube preferably used in this invention.

FIGURE 4 is a schematic diagram of the heat exa greater) Patented Dec. 1 5 1962 change fluid circulating system for maintaining the desired temperature gradient along the draw tube.

FIGURE 1 shows the manner in which a traveling yarn 10 is wrapped around the drawing tube 12. The angle B, i.e., the yarn approach angle with respect to the tube axis and the number of wraps which the yarn makes about the drawing tube are dependent upon the particular process conditions and the desired results of the drawing. To simplify the description of the operation of the drawing tube of this invention, it will be assumed that the tube is nearly vertical and that the yarn first contacts the tube at the bottom and leaves from the top of the tube. This position is not critical and the tube works equally as well in any position.

FIGURE 2 shows the temperatures along the tube length for both the yarn and the oil. Curve 14 shows the temperature of the yarn as it first contacts the tube at the bottom, moves around and up the tube, and leaves at the top of the tube. The heat transfer fluid, preferably oil, 16 flows counter to the yarn, i.e., it contacts the tube wall first at the top of the tube and flows down and leaves at the bottom of the tube. Curve 18 is a plot of the temperature of the oil along the tube length. As the yarn first engages the tube, it is heated due to the fact that the tube is hotter than the yarn at that point. At point A on the graph the yarn temperature and the oil temperature are equal. When the yarn starts drawing, heat is given off since drawing of synthetic .yarn during drawing. The tube may be rotated to vary the co-action with the yarn as desired.

FIGURE 3 shows the preferred embodiment of tube 12. The incoming oil 16 is forced through the center tube 20, through radial holes 22 to the narrow annular section 24, and thence out through hole 26.

As shown in FIGURE 4, the oil is recirculated at a 'constant rate by any suitable pumping means 28, fro-m the reservoir 30 through the tube 12 and returned to the reservoir 30. Temperature measuring means 32 controls electrical heaters 34 so that the oil temperature as it enters the tube is at the desired level.

The pump 28, reservoir 30, and heaters 34 can be located away from the tube or they can be mounted integrally with the tube into a single unit. Alternatively a single pump and heater arrangement can serve a plurality of yarn tubes. Also, a double threadline or other multiple threadline can be used satisfactorily in place of the single threadline disclosed.

The following illustrative example is given of one application of the present invention using an oil-heated drawing tube. A tube with an outside diameter of 3% inches, a wall thickness of inch, a length of 34 inches was used with 840 denier (92 tex), filaments, nylon yarn moving onto the tube at 1500 yards per minute and leaving the tube at 2300 yards per minute. The oil was recirculated at the rate of 6 gallons per minute through a narrow annulus which had a radial dimension of 0.030 inch. The heat transfer coefiicient under these conditions was above 500 p.c.u./(hr.) (sq. ft.) (C.) [equivalent to 500 B.t.u./(hr.) (sq. ft.) (l- The incoming yarn temperature was 162 C. and the yarn left the tube at 194 C. The oil was supplied at 192 C. and returned to the reservoir at C.

It will be seen that this invention provides a simple and compact arrangement for substantially simultaneously heating a moving yarn to the drawing tempera ture, drawing the yarn, and carrying away the excess heat. This is an arrangement which is economical to construct and maintain yet highly effective and reliable in operation.

It is to be understood that the foregoing description is by way of example only and that various modifications and changes in the details may be made without departing from the spirit of the invention and the scope of the following claims.

I claim:

1. An improved apparatus for treating a moving filamentary structure of synthetic polymeric material immediately prior to and during a drawing operation, said apparatus comprising an elongated cylindrical drawing element having a central axis and comprising single continuous peripheral surface for frictional contact with an axially spaced plurality of helical turns of a moving filamentary structure before and during a drawing operation on the structure, said surface of said element comprising a first peripheral portion and a second peripheral portion axially spaced therefrom, said element further comprising a heat exchange means contained therein for continuously removing excess heat from a moving filamentary structure in engagement with said first portion of said surface during a drawing operation on said structure, and simultaneously continuously transferring the excess heat back to the moving filamentary structure in engagement with said second portion of said surface just prior to the drawing operation to elevate the temperature of the structure to the desired drawing temperature prior to the drawing operation, said heat exchange means comprising a passageway constructed and arranged in operative heat exchange relationship with said first and second portions of said surface to conduct an elevated temperature heat exchange medium first into heat exchange relationship with said first portion and then into heat exchange relationship with said second portion, and means for controlling the temperature of said medium.

2. An improved method for continuously simultaneously treating a plurality of turns of a running yarn line of synthetic polymeric composition on a unitary elongated cylindrical drawing element immediately prior to and during a drawing operation, said element provided with a central axis and continuous exterior surface, said method comprising, in combination, the steps of maintaining a first heat input area on the exterior surface of said element at a first given temperature and an axially spaced second cooling area on the exterior surface of said element at a second given temperature, continuously moving a yarn in a plurality of axially spaced helical turns around and in engagement with the exterior surface of said element first over the heat input area and secondly over the cooling area in sequence, the first and second given temperatures maintained at levels with respect to the yarn temperature in each area such that heat generated by drawing of the yarn and by frictional engagement of the yarn with the element in the cooling area is continuously removed from the yarn and said cooling area and transferred axially of the element to the heat input area and the yarn in the heat input area to elevate the temperature of the yarn to the desired drawing temperature.

3. An improved apparatus for treating a moving filamentary structure of synthetic polymeric material immediately prior to and during a drawing operation, said apparatus comprising an elongated cylindrical drawing element having a central axis and comprising single continuous peripheral surface for frictional contact with an axially spaced plurality of helical turns of a moving filamentary structure before and during a drawing operation on the structure, said surface of said element comprising a first peripheral portion and a second peripheral portion axially spaced therefrom, said element further comprising a heat exchange means contained therein for continuously removing excess heat from a moving filamentary structure in engagement with said first portion of said surface during a drawing operation on said structure, and simultaneously continuously transferring the excess heat back to the moving filamentary structure in engagement with said second portion of said surface just prior to the drawing operation to elevate the temperature of the structure to the desired drawing temperature prior to the drawing operation, said heat exchange means comprising a passageway constructed and arranged in operative heat exchange relationship with said first and second portions of said surface to conduct an elevated temperature heat exchange medium into heat exchange relationship with said first portion and into heat exchange relationship with said second portion, and means for controlling the temperature of said medium.

Gabler Jan. 22, 1957 Boerma et al July 25, 1961 

1. AN IMPROVED APPARATUS FOR TREATING A MOVING FILAMENTARY STRUCTURE OF SYNTHETIC POLYMERIC MATERIAL IMMEDIATELY PRIOR TO AND DURING A DRAWING OPERATION, SAID 